The present invention relates to an optical beam scanner such as a laser copying machine, laser beam printer, etc.
For a laser beam printer or the like, an optical beam scanner is employed to perform the deflection scanning of the laser beam. FIG. 1 and FIG. 2 illustrate an example of the optical beam scanner employed for a laser beam printer. As shown in FIG. 1, a rotor unit 2 is arranged on the optical path of the laser beam emitted from a laser unit 1. To both units 1 and 2, a light source circuit board 1A and a scanner circuit board 2A respectively fixed, each with electronic circuits and others being arranged individually. In the boards 1A and 2A, electric connectors 1B and 2B are respectively installed to connect each of them with a control circuit which is not shown in FIG. 1.
Then, both units 1 and 2 are coupled to each other by a housing 3 as shown in FIG. 2. In the laser unit 1, a laser light source 11 is connected to the light source circuit board 1A electrically by soldering lead lines, etc. The semiconductor laser light source 11 is fixed to a base 12 with a spring member 13, and a through hole 14a is provided in a holder 14 which is mounted on the base 12 in such a manner that the position thereof can be adjusted. In this through hole 14a, a barrel 15 is installed slidably in the longitudinal direction. Also, in the barrel 15, a collimator lens 16 is installed to converge the light flux from the laser light source 11.
In assembling the laser unit 1, the holder 14 is mounted by adjusting to match the center axes of the through hole 14a and the collimator lens 16 on a jig which is not shown in FIG. 2, and while observing the shape of the laser beam to be emitted, the position of the base 12 is adjusted so that the base 12 and the holder 14 are fixed at an optimum position by screws, etc. to complete the adjustment of the optical axes of laser source 11 and collimator lens 16. The laser unit 1 already adjusted and the holder 14 are fixedly fitted into a laser unit installation hole 3a provided in the housing 3.
Meanwhile, in the rotor unit 2, a high-speed revolution motor 21 is electrically connected to the scanning circuit board 2A. On a rotor 22 fixed to the axis of the high-speed revolution motor 21, a rotary mirror 24 is fixed with a washer 23. The rotor unit 2 is fixed by fitting the high-speed revolution motor 21 into a rotor unit installation hole 3b provided in the housing 3.
The laser beam emitted from the laser unit 1 is incident on the reflecting mirror surface 24a and 24b of the rotary mirror 24, and the deflection scanning is performed by the rotation of the rotary mirror 24. While the scanning is performed on a photosensitive member 5 at a constant speed by the function of a f-.theta. lens 4, the positional adjustment of the laser unit and the rotor unit 2 has traditionally been made at this juncture in such a manner that the laser unit installation hole 3a and the rotor unit installation hole 3b provided in the housing 3 are machined under the severe precision control in manufacturing in order to obtain the accurate mounting positions and the center axis matching, and that when the laser unit 1 and the rotor unit 2 are just fitted into the laser unit installation hole 3a and the rotor unit installation hole 3b respectively, the optical position adjustment therefor is complete. Traditionally, therefore, the manufacturing of the housing 3 has been carried out often by machining an aluminum diecasting or forming a resin mold.
However, as the above describes, if the light source circuit board 1A and the scanner circuit board 2A are separated and are electrically independent, the connection to the control circuit, etc., which are not shown in FIG. 1, should be made separately, resulting not only in the increased number of lead lines but in the hindrance of the miniaturization and production efficience, not to mention the susceptivity to the noise problem, etc.
Also, in manufacturing the housing 3, aluminum should be machined to obtain the accurate angles and positions, which requires an extremely high manufacturing cost. For the manufacture by the use of the resin mold formation, which has been more widely employed in recent years in order to attempt the cost down and meet the requirements for a lighter weight product, it is necessary to use a highly precise metal die in view of the maintenance of the accurate pattern drawings and precision gradients and positions. This still requires an expensive manufacturing cost.
In this respect, therefore, an image formation apparatus is proposed as disclosed in Japanese Laid-Open Patent Application 1-251050, wherein a first circuit board having parts for a laser driving system and a second circuit board having parts for a scanning system are arranged in the housing of a laser exposure unit at shifted positions to each other, and these two kinds of cirucit boards are interrelatedly connected electrically and mechanically by the connectors provided on the respective circuit boards. The structure thereof is illustrated in FIG. 3.
Inside the housing main body 86, a laser driving assembly 150 and a mirror driving assembly 151 are arranged as shown in FIG. 3. On the printed-circuit board (the first circuit board) 152 which is the base for the laser driving assembly 150, a semi-conductor laser oscillator 153 as a laser light source, a collimator system optical unit 154 with built-in collimator lens and prism, and various electronic parts for the laser driving system, which form the circuits required to drive the laser oscillator 153, are installed. In addition, there is provided on this circuit board 152 a connector 155 having terminal pins to connect the laser driving assembly 150 to the mirror driving assembly 151 mechanically and electrically. The laser output end of the collimator system optical unit 154 faces the reflection surface of a polygon mirror 201.
In the mirror driving assembly 151, the polygon mirror 201 which constitutes a polygon scanner 200, a motor 202 for driving this mirror 201, and various scanner system parts required to control the rotation of this motor 202 are installed. The motor 202 is a brushless DC motor, for example. On the printed-circuit board (the second circuit board) 203 which is the base for the mirror driving assembly 151, a connector 204 is provided to connect with the connector 155 of the aforesaid laser driving assembly 150. The holes of the connector 204 are opened downwards. Consequently, the pins of the connector 155 of the laser driving assembly 150 are inserted from the lower side of this connector 204.
As the above describes, the two kinds of units 150 and 151 are connected with each other electrically and mechanically through the connectors 155 and 204.
Nevertheless, with the aforesaid laser exposure unit shown in FIG. 3, it is impossible to adjust 10 the positions of the boards themselves after having been connected because the two kinds of circuit boards are connected through the connectors. Therefore, it is necessary to machine and install the parts with high-precisions beforehand.
An object of the present invention is to solve each of the aforesaid problems and provide an optical beam scanner which is compact without any complicated wirings and which can be manufactured without such a high-precision machining.
In order to achieve the aforesaid object, an optical beam scanner according to the present invention is characterized in that in the optical beam scanning apparatus having a laser light source to output laser beam and an optical scanning unit to deflect the laser beam, a light source circuit board with the laser light source fixed thereto and a scanning circuit board with the optical scanning unit fixed thereto are connected electrically in such a manner that the positions thereof can be adjusted mechanically.
Since the optical beam scanner of the above-mentioned structure has the light source driving circuit and the scanner driving circuit on the same circuit board, or the light source circuit board and scanner circuit board are directly connected electrically, it is possible to unify the wirings for the connection of the control circuit, etc. 10 as well as to make the apparatus compact. Also, it is unnecessary to perform such a high-precision machining because the light source circuit board with the light source fixed thereto and the scanner circuit board with the optical scanning unit fixed thereto are directly connected in such a manner that the relative position thereof can be adjusted mechanically.